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Three-Mode Skin Probe Detects Cancer

Photonics.comAug 2014
AUSTIN, Texas, Aug. 6, 2014 — A new device could potentially allow doctors to get a clearer picture of cancerous skin lesions and reduce the number of unnecessary biopsies.

A team at the University of Texas at Austin has developed a probe that combines three distinct spectroscopy methods to measure the properties of skin tissue: Raman spectroscopy, diffuse reflectance spectroscopy and laser-induced fluorescence spectroscopy. The 3-in-1 device offers a fast, comprehensive and noninvasive examination of melanoma and other skin cancer lesions.

This schematic shows the front of the new probe (left), as well as the probe assembly with its optical elements (right). Courtesy of E.Marple/EmVision LLC.
The probe reveals information invisible to the human eye that can offer a better screening tool for cancer and eliminate many negative biopsies, according to the researchers. They noted that as normal skin becomes cancerous, cell nuclei enlarge, the top layers of skin thicken, and the skin cells can increase their consumption of oxygen and become disorganized. These changes alter the way light interacts with the tissue.

In particular, diffuse optical spectroscopy can be sensitive to absorption by proteins such as hemoglobin, while Raman spectroscopy is sensitive to vibrational modes of chemical bonds, including those found in connective tissues, lipids and cell nuclei.

At present, the only definitive way to diagnose skin cancer is to perform a biopsy, according to the researchers.

The entire 3-in-1 spectroscopy system, in more detail. Courtesy of M.Sharma and J.Tunnell/University of Texas at Austin.
However, determining which lesions to biopsy can be imprecise: For every case of skin cancer detected, roughly 25 negative biopsies are performed. The researchers noted that this can be quite expensive and sometimes unnecessarily time consuming.

“Skin is a natural organ to apply imaging and spectroscopy devices to because of its easy access,” said researcher James Tunnell, an associate professor of biomedical engineering at UT. “This probe that is able to combine all three spectral modalities is the next critical step to translating spectroscopic technology.”

Acronym for profile resolution obtained by excitation. In its simplest form, probe involves the overlap of two counter-propagating laser pulses of appropriate wavelength, such that one pulse selectively populates a given excited state of the species of interest while the other measures the increase in absorption due to the increase in the degree of excitation.

That branch of spectroscopy concerned with Raman spectra and used to provide a means of studying pure rotational, pure vibrational and rotation-vibration energy changes in the ground level of molecules. Raman spectroscopy is dependent on the collision of incident light quanta with the molecule, inducing the molecule to undergo the change.